Dental impression material



' Patented Feb. 10, 1942 3 OFFICE DENTAL IMPRESSION MATERIAL Stanley E. Noyes, Los Angele's, Calif.

N Drawing.

Application March 12, 1938,

Serial No. 195,541

Claims.

This invention relates to a dental composition, and more specifically it relates to a composition of matter suitable for use by dentists or dental technicians in making impressions of the teeth and gums.

For many dental purposes such as the making of full or partial dentures, bridges, inlays, etc. it is me essary for the dentist to be able to accurately reproduce portions of the mouth of the subject. Such reproductions often involve the duplication of undercuts of more or less severity, as for instance in cases where a tooth or teeth have been extracted and the adjacent teeth have crowded together.

Impression materials such as plaster of Paris or the various shellac and wax compositions, which have been used for many years, have little or no elasticity, making reproduction of undercuts very.

difiicult, the procedure involving either breaking the impression and re-assembling it, as is done with plaster, or taking the impression in sections as is the practice with shellac and wax compounds. Such methods are obviously time consuming, and

jured when handled, and have contained so much water. that great care was necessary to prevent involve danger of inaccuracy and discomfort to the patient. By the use of an impression material which may be introduced in the mouth in a fluid or plastic condition and cooled to an elastic state, it is possible to take animpression which accurately reproduces all details of the portion of the mouth under examination, and which due toits elasticity, can be removed from any undercuts present without losing the accuracy of the impression.

Due to the narrow range of temperature which the human mouth can stand, rather strict limitations'are placed on the types of elastic materials which can be used. These materials must obviously be either fluid or plastic when they. are seated to place in the mouth, and must change by cooling to elastic gels which will permit removal from the undercuts without permanent distortion. They must also be sufficiently tough and rigid so that they may be used as molds for models of plaster or other compounds to be poured into them. I v

It'is possible by the use of a hydro-colloid to obtain a compound which is a viscous fluid when slightly warmed, and which cools at mouth temperature or by the use of ice water to a gel which is sufficiently elastic to reproduce undercuts properly, and which can with care be handled and used as a mold to receive plaster. Several such hydro-colloid compositions have been proposed, usually using agar-agar as a base. have all been relatively fragile'and easily in- They evaporation from the impression with accompanying change of shape or size. Some of them have contained added ingredients such as copal, pontianak, balata, rubber-latex and polymerized rubber to toughen them, and some have contained added materials such as potassium sulphate to facilitate the set-of plaster against the surface of the impression.

My invention provides an impression material having elastic properties as above mentioned, but in addition having greatly increased strength and toughness to facilitate handling of the impression, having less tendency to change in'shape or size by evaporation of water from the impression, and having a surface against which plaster of Paris sets satisfactorily.

Agar-agar, when dissolved in water, forms gels at very low .concentrations, a 1% solution setting to a fairly stifl. jelly. Ordinary dental impression materials using an agar-agar base, use this in proportions of one part agar-agar to from 10 to 15 parts of water, giving a stiff gel, but one from which water evaporates readily with resulting change inshape or size. My invention provides for a composition with a preferred proportion of 1 part agar-agar to from 8 to 10 parts of water,

which greatly reduces the tendency for the water Ordinary dental impression materials ofthe hydro-colloid type are fragile, thin sections breaking readily when sharply bent, and requiring very great care in handling. My invention provides for the use of esters of polyhydric alcohols and boricacid as plastici'zing and toughening agents, by which use the material is so toughened that thin sections may be bent double without breaking.

Such toughened hydro-colloid gels alone will not permit plaster to set satisfactorily against their surfaces, the surface of the plaster being soft and spongy. It is possible to dip or otherwise coat the gel surfaces with acids or solutions of salts such aspotassium sulfate or alum to aid the set of plaster; andin fact this is often done with ordinary impression materials of the hydrocolloid type, but this is a troublesome extra operation, and is liable to render the impression less accurate. My invention provides for" the incor- Grams Agar-agar 450 Water 4400 Manganese sulfate (anhydrous) 200 Red iron oxide 12 Titanium oxide 18 Salicylic acid 1 Glycol bori-borate 400 Oil of Wintergreen The foregoing materials in the proportions shown are compounded as follows: The 'agar,

water, '70 gm. of the manganese sulfate, and all of the iron oxide, titanium oxide and salicylic acid are placed in an autoclave, and heated with agitation at approximately 235 deg. F. for approximately an hour and a half. Too long heating or too high a temperature tends to lower the viscosity of the mixture and render it too fluid for use, and the time and temperature of heating also requires adjustment for the grade of agaragar used. The iron oxide and the titanium oxide are introduced to color the mixture, and may be omitted if desired or other materials substituted. The salicylic acid is used to sterilize the material and prevent growth of molds or bacteria if any of it is allowed to stand exposed to the air, and may also be omitted if desired or other materials submitted.

After the heating period is complete, the autoclave is allowed to cool to 212 F. or below, and is opened, the glycol bori-horate added and mixed in, then the remaining manganese sulfate and the oil of Wintergreen, and after thorough mixing, the material is run into cans, tubes, or other containers. The oil of Wintergreen is used merely to impart flavor and odor, and other materials for this purpose can be substituted if desired.

Various esters of boric acid with glycerol, polyglycerol, mono, di and tri ethylene glycol, etc.

with or without the addition of borax can be used as plasticizers and toughening agents, the

proportions being suitably varied forthe particular compound used to secure the strength and stiffness desired.

Various materials other than manganese sulfate can be used as hardening agents for plaster, such as copper sulfate, aluminum sulfate, ferric sulfate, zinc sulfate, zinc chloride, and other salts of di or trl-valent metals which facilitate the setting of plaster without reacting with the hydro-colloid to render it insoluble or too greatly lowering the viscosity of the composition when warmed. However, I find that manganese sulfate is the preferable material to be used for this purpose and particularly anhydrous manganese sulfate. Salts of the alkali metals such as sodium chloride or potassium sulfate have not proven satisfactory, as when used in sufficient quantity to permit plaster to set properly, they have too great an effect on the viscosity of the composition. Other hydro-colloids such as karaya, casein, gelatin, pectin, etc. may be used to replace part or all of the agar-agar, but for most purposes, the latter is to be preferred.

The above composition is adapted to become plastic within a temperature range comfortable to the mouth, 1. e. between approximately -135 F. and to set-to an elastic gel when allowed to cool to approximately body temperature. In using it, the dentist usually places a collapsible tube of the material in hot water, which may be boiling if desired, allows the heat to penetrate and soften the material, removes the tube from the water and allows it to cool to F. or below. He then opens the tube, loads a dental tray or appliance suitably with the plastic material, seats it to place in the mouth, and holds the tray without permitting movement while the impression material cools from the plastic to the elastic gel state. This usually requires three to five minutes, and gelling may be aided by the use of cold water if desired. The tray containing the impression is then removed from the mouth and used for a mold for casting plaster of Paris or in any other way desired. Instead of using material in tubes, portions of the material may be softened by heating in a double boiler or any suitable mixer. It is obvious that the material may be used for many other purposes where it is necessary to make an accurate reproduction of an object, as for instance the reproduction of dental models, the taking of facial impressions, the taking of impressions for fitting surgical appliances and the duplication of art objects or ornaments.

It is obvious that by varying the proportions and ingredients, mentioned, the properties of the composition may be altered over a considerable range, and I do not wish to be limited by the example given as it is merely illustrative of the invention.

By the use of manganese sulfate in conjunction with agar-agar or other reversible gelforming organic hydro-colloid bases, but omitting the glyco-borate it is possible to increase the plaster setting qualities without increasing the toughness of the product. For example if 450 gm. of agar-agar, 4400 gm. of water and 100 gm. of manganese sulfate is compounded in the manner described in the preceding example the product obtained has excellent plaster setting qualities.

In the foregoing example I have set forth the use of 200 grams of anhydrous manganese sulfate in conjunction with 450 grams of agar-agar and 4400 grams of water. That amount of manganese sulfate is the preferred quantity to be employed with 450 grams of agar-agar and 4400 grams of water, however, I find that I may'use as little as 100 grams or as much as 300 grams of the anhydrous manganese sulfate in the composition.

In the preceding disclosure I have described mixing the ingredients of my plastic composition under pressure in an autoclave. I may also prepare the composition by mixing the components in an open vessel under ordinary atmospheric pressure and at a temperature of about 212 F however, I prefer to mix under pressure.

In the preceding disclosure I have described the use of various esters of boric acid to be employed as toughening agents in my impression composition. Besides these esters I may also employ alkali metal perborates such as sodium and potassium perborate as toughening agents in impression composition.

I claim:

1. An impression material comprising a reversible gel-forming organic hydro-colloid base, a reaction product of a polyhydric alcohol and boric acid and the sulfate of one of the metals selected from the group consisting of manganese, aluminum, zinc and iron.

2. An impression material comprising a reversible gel-forming organic hydro-colloid base, a reaction product of a polyhydric alcohol and boric acid and manganese sulfate.

3. A composition as claimed in claim 2 in which thehydro-colloid base is agar-agar.

4. An impression material comprising one part of a reversible gel-forming organic hydrocolloid base, not over 10 parts of water and a reaction product of a polyhydric alcohol and boric acid.

5. An impression material comprising one part of a reversible gel-forming organic hydrocolloid base, not over 10 parts of water, a reaction product of a polyhydric alcohol and boric acid and the sulfate of one of themetals selected from the group consisting of manganese, aluminum, zinc and iron.

6. An impressionmaterial comprising a reversible gel-forming organic hydro-colloid base, glycol bori-borate and manganese sulfate.

7. An impression material comprising a reversible gel-forming organic hydro-colloid base, glyceryl borate and manganese sulfate.

8. An impression material comprising approximately 9 parts of agar-agar, 88 parts of water,

STANLEY E. NOYES. 

